We have found that cells from a patient with Fanconi's anemia are deficient in their ability to excise UV-induced pyrimidine dimers and covalently bound carcinogens from their DNA. We have also found that the physical properties of DNA extracted from these cells differes from normal. We wish to further study these abnormalities by a more extensive characterization of the DNA and the proteins with which it is associated in Fanconi's anemia cells. We wish also to further characterize the metabolic aberrations responsible for the failure of these cells to excise DNA damage We also wish to determine whether or not the findings in this one individual occur generally in patients with Fanconi's anemia. Because patients with Fanconi's anemi and their near relatives have an increased likelihood of developing neoplastic disease and chromosomal instability, we except that these studies, and subsequent one based upon them, will add to our understanding of noplastic transformation as well as to our understanding the mechanisms of chromosome instability and the role that chromosomal aberrations play in the pathogenesis of Fanconi's anemia.